Continuous Spin Particles and New Physics at Low Energies

by Shayarneel Kundu

Friday 17 Apr 2026, 12:30 → 14:30 America/Los_Angeles

48/2-224 - Madrone (SLAC)

The most general massless particle admitted by Lorentz Invariance and Quantum Mechanics is the “Continuous Spin Particle” (CSP). A CSP has an infinite number of discretely spaced helicity states which mix under the little group, and hence under Lorentz transformations. The magnitude of mixing is controlled by a new fundamental parameter, the spin-scale - $\rho$. The free field theory, its interactions and preliminary phenomenology was introduced over the past decade. The observables computed demonstrate a trend of recovering the physics similar to that of familiar massless particles at high energies, with deviations at lower energies. In this talk, I will talk about the leading order corrections to CSP mediated gravity, and the interaction of a CSP with a spinning degree of freedom and some of its simple phenomenology, noting that in both cases, the observables show a deviation from expectations at low energies.

CSP-SLAC-Seminar.key